Arthrogryposis, also known as arthrogryposis multiplex congenita or AMC, is a birth defect in which a child has various joints that are tight (contracted) with decreased motion, stiffness, deformity, and difficulty with function. The incidence for this is one in 3,000 live births. It is not a progressive disorder. In some cases, arthrogryposis is inherited and is passed from one generation to the next. In other cases, there is no explanation for the decreased movement of the fetus while in utero. Arthrogryposis encompasses a spectrum of musculoskeletal joint contractures from general joint immobility/tightness to rare syndromes creating difficulty with walking, mobility and function. The one thing that they all have in common is weak muscles and stiff joints.
The clinical findings of arthrogryposis are due to fetal akinesia. There are multiple proposed mechanisms that result in a lack of fetal motion: failure of skeletal muscle development, anterior horn cell abnormalities, vascular interruption, defective myogenic regulatory genes resulting in defective somites, maternal antibodies to fetal acetycholine receptor (as in maternal myasthenia gravis) and possible infectious viral causes (Hall, 1997; Swinyard, 1985). About 93% of cases are thought to be neuropathic (abnormal anterior horn cells) and 7% myopathic.
Distal arthrogryposis has been linked to autosomal dominant transmission. Most forms of amyoplasia are idiopathic, and there is no known genetic cause. The incidence of arthrogryposis is 1 in 3000 births. The incidence of true amyoplasia is 1 in 10,000 births
Types of Arthrogryposis
There are four main types of arthrogryposis:
Amyoplasia: Babies diagnosed with amyoplasia have dense fibrous tissue and fat instead of skeletal muscle. This leads to a loss of muscle development and poor range of motion and deformity in most joints.
Distal arthrogryposis: This type affects only several joints, usually in the hands and feet, and range of motion may be mildly limited.
Classic arthrogryposis: This type usually affects the hands, wrists, elbows, shoulders, hips, feet and knees with varying severity. The most severe cases can affect almost every joint, including the back and jaw. A loss of joint motion is frequently accompanied by muscle weakness.
Syndromic arthrogryposis: This type affects internal organs, as well as the muscle and joint systems. It can cause breathing problems, feeding problems, speech disorders and, in some cases, development delays.
Here, the ring and tiny fingers are more straight due to arthrogryposis on the palm’s top.
Risk factors and primary prevention
AMC occurs from 1/3000 to 1/5000 live births. Males and females are equally affected. Muscle disorders, muscular dystrophies, mitochondrial disorders, neural tube defects, or other PNS and CNS disorders are at an increased risk for AMC. Neurogenic factors are the most common cause of fetal akinesia presented in 70-80% of AMC patients.
Other risk factors include maternal illnesses, such as multiple sclerosis, diabetes mellitus, myasthenia gravis, and maternal hyperthermia in the first trimester. Severe bleeding during pregnancy or after a failed attempt at pregnancy termination, metabolic disease such as phosphofructokinase deficiency and drugs taken during pregnancy (e.g., muscle relaxants, misoprostol, cocaine, alcohol) can also be associated with arthrogryposis. Additionally, maternal Zika virus infection is the most frequent viral infection causing AMC and CNS anormalis with 30% of affected newborns with bilateral or unilateral hip, knee, hand and /or foot contractures.
Regular prenatal care assists with early diagnosis of decreased fetal movement but does not decrease incidence or improve outcome.
Causes of Arthrogryposis
In most cases, the exact underlying cause of arthrogryposis is unclear. However, the most common possible causes of arthrogryposis include:
- Limitation of your baby’s movement caused by insufficient amniotic fluid, another baby in the uterus or an unusually shaped uterus. If your baby can’t move their joints, then excess tissues form around those joints.
- A maternal disorder like multiple sclerosis. Your risk of multiple sclerosis increases if someone in your family has it.
- A genetic disorder like muscular dystrophy.
- Diseases of your central nervous system, including Moebius syndrome and spina bifida (meningomyelocele).
- Diseases of your neuromuscular system, including myasthenia gravis.
- Diseases of your connective tissues, including dysplasia and metatropic dwarfism.
In some cases, the cause of arthrogryposis is likely a combination of genetic and environmental issues.
Children with AMC may be diagnosed before birth on ultrasound or shortly after birth. Symptoms vary depending on the specific diagnosis but commonly include:
Stiff joints of the arms and/or legs (joint contractures) All 4 limbs are affected in 84%, just the upper extremities in 11 %.
- Head and neck normal
- Normal or above-average intelligence
- Limited fetal movement during pregnancy
- Small size
- Decreased amount of muscle
- Absent skin creases at joints
- Delayed development such as sitting up or standing
- Abnormalities of feet (ex: clubfoot)
- Characteristic birthmark on the face
- Hips are often flexed and dislocated
- They sometimes have scoliosis
Distal arthrogryposis is an important type of arthrogryposis. In these children, the knees and elbows are relatively spared, and the hands and feet are more affected. There are more than 20 different subtypes of distal arthrogyposis, and the face and neck be affected in some.
Complications of Arthrogryposis
Common characteristics and complications associated with arthrogryposis:
- Dislocated hips
- Facial asymmetry
- Facial birthmarks
- Hand contractures
- Internally rotated shoulders and limbs
- Intestine, kidney, bladder and genital malformation
- Muscle absence or atrophy
- Respiratory problems and aspiration of fluids
- Webbed and/or dimpled skin
A baby born with Arthrogryposis
Diagnosis and test
In some cases, arthrogryposis isn’t spotted during pregnancy. But your baby’s doctor can usually diagnose it during an early physical exam. In order to make the most accurate diagnosis, your doctor may also order tests such as:
- MRI (to see if any organs in the body are affected)
- CT scan
- Biopsy (small tissue sample) of a muscle to see if the muscle fibers are normal
- Blood tests to look for any gene variations or atypical chromosomes that may indicate another disease
Treatment for Arthrogryposis
Treatment for arthrogryposis should be started as soon as possible. In some cases, the newborn may need immediate care in our Newborn Intensive Care Unit (NICU). Our NICU provides specialized care for babies born with serious health conditions.
Early treatment for arthrogryposis is often very successful, and most children with this condition live satisfying and productive lives. Depending on the extent and type of your child’s syndrome, they may have one or more of these treatments:
Physical therapy (PT): This includes exercises, stretches and other movements to increase your child’s muscle strength and range of motion. PT can also help with gross motor skills such as learning how to roll, crawl, sit, stand, walk, use crutches and other ways of being mobile.
Occupational therapy (OT): Occupational therapists help children learn ways to take care of themselves. If your child needs a wheelchair or walker, our OT can help them learn how to use it. OTs also help children with fine motor skills such as writing and using utensils to eat.
Splinting and casting: These are used to hold a joint in place, to stretch the tissues in a joint or to line up bones so the child can move more easily. Splints can be changed as your child’s range of motion improves. In some cases, splints are worn only at night. Your child may be referred to an orthotist who will make these splints.
Surgery: When other treatments have not worked, or when the child has reached optimal improvement with other therapies, your child’s specialist may recommend a surgical procedure. The surgical team at Phoenix Children’s has the skills and experience to provide safe surgeries with excellent results. For children with arthrogryposis, the team usually consists of orthopedic and plastic surgery teams working together.
Surgery for arthrogryposis can include procedures to:
- Shorten, lengthen or change the position of a bone to improve how joints line up.
- Release a joint capsule if it is restricting movement.
- Release or lengthen tendons or muscles.
- Transfer tendons or muscles to help improve function
- Correct clubfoot, hip dysplasia or scoliosis related to arthrogryposis.
If your child’s arthrogryposis includes severe nervous system involvement, the specialists in our Neuromuscular Clinic can provide the necessary care for the best outcome.
Currently, Arthrogryposis Multiplex Congenita may not be preventable.
- If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
- Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders
Regular medical screening at periodic intervals with tests and physical examinations are recommended.